AquaVIT-4: International Intercomparison of atmospheric water-vapor instruments

The AquaVIT-4 campaign aims to compare state of the art and new atmospheric hygrometers with each other and with traceable humidity standards at the aerosol and cloud simulation chamber AIDA (Karlsruhe Institute of Technology, Germany, ).

The campaign will be held on beginning of 2022 (dates to be defined). This campaign is part of a project that has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 730997.”


The present campaign is built in the frame of the HEMERA H2020 european project, a new research infrastructure involving a large community in balloon-borne researches. In the frame of the WP 11 “Innovation on sensors and algorithms for balloon-borne research”, this proposal focuses on the JRA 2.1 and 2.2, which aims at defining standards and protocols for balloon measurements relevant for Copernicus and a set of Light Innovative Instruments (SLII) for transnational access (TNA) payload and data during TNA flights. AquaVIT-4 aims to support newly developed european hygrometers in their calibration efforts against reference and well-known instruments.

Figure 1: Picture of the AIDA facility.

This campaign would be one piece of a larger project which aims at including metrological institutes to help defining good practices and standards for essential climate variables, facing the need of increasingly accurate and precise atmospheric data.

The campaign practical objectives are:

  • To provide a continued basis for quality control of airborne hygrometer measurements.
  • To document the improvement of existing hygrometers and the allow the testing of new instruments related to the JRA 2.1 / 2.2 of Hemera EU project (

The campaign will be split into two phases :

  • Quick look data (week 1): Preliminary measurements will be made available to the referees as soon as possible following each day’s experiments (<24 h). This step will allow, in case of difficulties, to suggest corrections to data processing, instrument configuration, or instrument operation to improve the overall outcome of the intercomparison.
  • Blind comparison (week 2) : blind measurements will be quickly release (within 2 months), together with preliminary data to be made available only to the referees (O. Möhler, K. Rosenloff , M. Fujiwara and E. Georgin (to be confirmed)) who are not affiliated with any participating instrument team. The referee board, will therefore perform a short evaluation (within 2 months).

At the end of the short evaluation period, datasets will be release to all participants. After careful checking from respective participants, final datasets will be made available to the AERIS data portal.

Participants :

AquaVIT-4 gathers 22 participants from 9 laboratories in the USA, Europe and Russia. A list of the participants is shown in the table below together with the hygrometers and their location in the chamber.

Potential participantAffiliationInstrumentLocation at AIDA*
Harald Saathoff,
Robert Wagner
Ottmar Möhler
KIT, DTDL (1370 nm) for measurements in AIDA (gas phase water only) APicT

TDL (1370 nm) for measurements outside AIDA (total water) APeT

Harald Saathoff,
Robert Wagner
Ottmar Möhler
KIT, DDew point mirror MBW-373LX, FTIR (ice water content)
Teresa Jorge,
Nico Germann,
Frank Wienhold
ETH Zürich, CHPCFH, frost point mirror (2)1
Teresa Jorge,
Nico Germann,
Frank Wienhold
ETH Zürich, CHPCFH, frost point mirror2
Nadir Amarouche,
F. Frérot,
M. Ghysels-Dubois#,
G. Durry
Albert Hertzog,
Claire Cenac,
Julio Lopez,
Paul Monnier
LMD, (DPAO), Palaiseau Cedex, FRSAWfPHY -IN1
Ivan Formanyuk,
Alexey Lykov
Central Aerological Observatory (CAO), Moscow, RUFLASH (A)3
Dale Hurst,
Emrys Hall,
Allen Jordan
Manuel Béla Tuzson, Simone Brunamonti
EMPA, Dübendorf, CHLightweight Mid-IR Laser Spectrometer3

*Options: 1) inside the vessel, 2) outside the vessel in the cold part, 3) heated sampling line to the warm laboratory.#PI.